In the design of compact printing devices, and, particularly, where the printing devices must operate at a relatively high speed, it has been the practice to provide a plurality of character rings on a rotatable shaft, each of the character rings having type characters on the periphery thereof. A selection mechanism provides for rotating each of the character rings into a position such that a selected character on each of the rings is in position for printing, at which time a printing hammer brings the inked character in contact with paper to effect the printing operation.
In an apparatus as described above, an electro-magnet conventionally is utilized to activate the selection mechanism, the activation following on the input of an electrical pulse to the electro-magnet. Where the electro-magnet itself moves the selection mechanism by way of a core in the electro-magnet, the electro-magnet must be relatively large and high-powered. These requirements are incompatible with the objectives of economy of size, weight and power consumption. Moreover, large-sized electro-magnets generate considerable noise and vibration during the operation thereof, these being substantial disadvantages. As is evident then, an improved means of driving the selection mechanism in a printing device is greatly to be desired.